EP1538737A1 - Control electronic and process for controlling an electric motor - Google Patents

Abstract

Drive electronics for driving an electric motor has control devices (31-34) which allow the power supply to the motor to be adjusted depending on the load acting on the motor. The control devices comprise an evaluation unit (31,32,35), and an adjustment device (33,35) for adjusting the power supply of the motor (20). Independent claims are included for the following: (1) An actuator with an electric motor. (2) Application of the drive electronics.

Description

The invention relates to a control electronics for controlling an electric motor according to the preamble of claim 1 and to a method according to Preamble of the independent method claim.

Control electronics and method of the aforementioned Kind be u.a. used in electric motors, the part of actuators are and the controlled setting of serve movable components in motor vehicles, For example, to operate flaps in the air conditioner. The disadvantage is that the motors in the control Vibrations can produce the unwanted Cause noise development. So is the air conditioning Usually housed in a housing, which is a kind Resonance box forms. It was found that the Vibrations which occur during the operation of the electrical Motors are generated, reinforced by the case so that they can become overly and by the Car occupants as annoying perceived noise to lead.

To reduce the generated during the control Vibrations, it is known, the electric motor in the To control stepper operation and the drive current in the Motor windings within a step sinusoidally too vary. But this has the disadvantage that the necessary control electronics additional, relatively expensive Components needed to handle the current in the motor windings to be able to record continuously.

In addition, an electric motor, which for Adjustment of moving components in motor vehicles is used, so to control that even with changeable external conditions such as ambient temperature (hereinafter also called Ta) and supply voltage (hereinafter also Vs called) a reliable operation is guaranteed. The Supply voltage for the electric motor, which of the Battery of the motor vehicle is delivered, as well as the Temperature Ta outside on the electric motor can be subject to considerable temporal fluctuations. Usually, it is required for motor vehicles that the Setting a movable component for temperatures Ta in the range of -40 degrees Celsius to 85 degrees Celsius and for a supply voltage Vs in the range of 9V to 16V reliable should work.

Based on this prior art, it is the task of present invention, a control electronics and to specify a method, which or a noise-reduced and reliable control of a electric motor allows and as simple and as possible is inexpensive.

This object is achieved by an inventive Control electronics according to claim 1 or by a Inventive method according to the independent Procedure claim solved. The further claims give preferred embodiments, an actuator with a according to the invention control electronics and a Use on.

The invention is based on the recognition that the electric motors, as in actuators for Motor vehicles are used, usually in oversized manner are controlled. Known controls are designed so that the engine even under the "worst" external conditions - i. according to the above example at Ta = 85 degrees Celsius and Vs = 9V - generates sufficient torque. Under normal external However, conditions that usually prevail are those of Motor generated torque or the achieved performance much too high, so that vibrations or noises in increased mass be produced and the balance of Expended and required energy is bad.

Fig. 1 schematisch einen Aktuator mit einer erfindungsgemässen Ansteuerungselektronik;

Fig. 2 ein Beispiel des zeitlichen Verlaufs einer Last auf einen elektrischen Motor und den zeitlichen Verlauf der Drehgeschwindigkeit, welche sich beim Rotor bei der Ansteuerung gemäss einem ersten Ausführungsbeispiel des erfindungsgemässen Verfahrens einstellt;

Fig. 3 die zeitliche Änderung der Spannung in den Motorwicklungen bei der Ansteuerung gemäss dem ersten Ausführungsbeispiel des erfindungsgemässen Verfahrens;

Fig. 4 ein Zeigerdiagramm zur Erklärung eines zweiten Ausführungsbeispiels des erfindungsgemässen Verfahrens;

Fig. 5 einen Aktuator mit einer erfindungsgemässen Ansteuerungselektronik;

Fig. 6 schematisch eine Klimaanlage eines Kraftfahrzeuges, für welche das erfindungsgemässe Verfahren bzw. die erfindungsgemässe Ansteuerungselektronik verwendbar ist; und

Fig. 7 schematisch einen Querschnitt durch das Gehäuse einer Klimaanlage.

The invention will be explained below with reference to embodiments with reference to figures. Show it

1 shows schematically an actuator with an inventive control electronics;

2 shows an example of the time profile of a load on an electric motor and the time profile of the rotational speed, which adjusts itself in the case of the rotor during activation according to a first exemplary embodiment of the method according to the invention;

3 shows the change with time of the voltage in the motor windings during the activation according to the first exemplary embodiment of the method according to the invention;

Fig. 4 is a phasor diagram for explaining a second embodiment of the inventive method;

5 an actuator with an inventive control electronics;

6 shows schematically an air conditioning system of a motor vehicle for which the method according to the invention or the control electronics according to the invention can be used; and

Fig. 7 shows schematically a cross section through the housing of an air conditioner.

Fig. 1 shows an electric motor 20 and a so connected control electronics 30. They are shown in FIG. 1 shown example components of an actuator 10, the over a bus line 11 having a central control unit 14 and via supply lines 13a and 13b with a Power supply unit 12 e.g. in a form of a battery connected is. The electric motor 20 is a brushless one Motor and includes stator windings 22a, 22b and a rotor 23 with permanent magnets. For controlling the electrical Motors 20, the stator windings 22a and 22b in a energized certain time sequence, so that the rotor 23 in Rotation is offset. Depending on the type of control, the electric motor 20 e.g. as stepper motor or as brushless DC motor can be operated.

The control electronics 30 comprises a central Computer unit 31 (e.g., microprocessor), a Memory unit 32, a circuit 33 with transistors, the during the energization of the windings 22a, 22b coordinated in time be opened or locked, a pulse generator 34, with which pulses can be generated to open or lock the Transistors in the circuit 33, and detection means 35 for detecting the voltages on the windings 22a, 22b and / or flowing through the windings 22a, 22b Current.

The control electronics 30 is preferably as an IC ("integrated circuit"), in particular ASIC ("application specific integrated circuit ").

The drive electronics 30 and the electric motor 20th together form a control loop. As a rule, a Parameter used, which of the on the engine 20 acting load is dependent, for example, the Rotational speed of the rotor 23 or the load angle. When Manipulated variable is the current level in the motor windings 22a, 22b used. In the control is the controlled variable Recurring determined ("actual value"), with a predetermined Reference value compared and the manipulated variable corresponding to Deviation between actual and setpoint ("control deviation") set. This type of scheme has the advantage that the torque generated by the motor 20 to the torque can be adjusted, which at the momentary load is needed to turn the rotor 23 in rotation offset. This can prevent the motor 20 too high torques generated that are not necessary would be to rotate the rotor 23 at the instantaneous load. By reducing the torque to the moment Required mass can be generated by the motor 20 vibrations be reduced, resulting in a much reduced noise Operation is possible.

When using the control electronics 30 in one Actuator 10 for adjusting a movable component in a motor vehicle, the setpoint for the controlled variable is so set the engine 20 in a certain range the supply voltage Vs and the ambient temperature Ta (according to above example 9V <= Vs <= 16V and -40 degrees Celsius <= Ta <= 85 degrees Celsius) works reliably. In particular, should be guaranteed that the engine 20 at the "most extreme Conditions "(Vs = 16V, Ta = 85 degrees Celsius) not overheated and in the "worst" conditions (Vs = 9V, Ta = 85 degrees Celsius) still the necessary torque for Adjustment of the movable component is generated.

Below are two embodiments of the method for driving an electric motor 20 explained.

1st embodiment

As a controlled variable, the rotational speed ω of the rotor 23 is used and the desired nominal rotational speed ω _{0 is} specified. Furthermore, a minimum rotational speed ω _{min can be} preset which, as explained below, serves to detect a maximum possible rotation of an actuating element connected to the motor 20.

The electric motor 20 is by means of Control electronics 30 driven by autocommutation and is thus used as a brushless DC motor. With this type of control, the motor windings 22a, 22b are not energized with a fixed step frequency, but a parameter is determined at each step, which is the time to carry out the next step sets. As a parameter, e.g. the current position of the rotor 23.

• Beim ersten Aktivieren des Motors 20 werden die Wicklungen 22a, 22b kurzzeitig bestromt, um den Rotor 23 vorerst in einer bestimmten Position festzuhalten.
• Dann wird der Autokommutationsmodus eingeschaltet. Dabei erfasst die Ansteuerungselektronik 30 wiederkehrend die momentane Drehgeschwindigkeit ("Istwert"), bestimmt die Abweichung von der Solldrehgeschwindigkeit und führt eine Regelung nach folgenden Kriterien durch:
• a)Ist die momentane Drehgeschwindigkeit kleiner als der Sollwert ω₀, wird der Strompegel erhöht, um eine Erhöhung des vom Motor 20 erzeugten Drehmoments zu erzielen.
• b)Ist die momentane Drehgeschwindigkeit grösser als der Sollwert ω₀, wird der Strompegel verringert, um eine Reduzierung des vom Motor 20 erzeugten Drehmoments zu erzielen.
• c)Ist die momentane Drehgeschwindigkeit kleiner als die minimale Drehgeschwindigkeit ω_min, befindet sich das mit dem Motor 20 verbundene Stellelement im Anschlag und die Stromversorgung des Motors 20 wird gestoppt.

The motor 20 is controlled or regulated as follows:

• When the motor 20 is first activated, the windings 22a, 22b are momentarily energized in order to hold the rotor 23 in a certain position for the time being.
• Then the auto-commutation mode is turned on. In this case, the control electronics 30 recurrently detects the instantaneous rotational speed ("actual value"), determines the deviation from the nominal rotational speed and carries out a control according to the following criteria:
• a) If the instantaneous rotational speed is less than the target value ω ₀ , the current level is increased to achieve an increase in the torque generated by the motor 20.
• b) If the instantaneous rotational speed is greater than the target value ω ₀ , the current level is reduced to achieve a reduction in the torque generated by the motor 20.
• c) If the instantaneous rotational speed is less than the minimum rotational speed ω _min , the actuator connected to the motor 20 is in abutment and the power supply of the motor 20 is stopped.

To control the current level is as a pulse generator 34 a Chopper uses, by which means Pulse width modulation pulses can be generated. By the Pulses are controlled by the transistors in the circuit 33 in a certain frequency (eg 20 kHz) and open locked, so that the energization of the windings 22a, 22b per Step is interrupted several times. By enlarging or Decrease the duty cycle while the transistors can be opened within a cycle, the Current level and finally the generated torque be set.

Fig. 2 shows in the lower curve 40 an example of the temporal change of the load, L, and in the upper curve 41 the associated temporal course of the Rotational speed in the control. The horizontal axis corresponds to the time t.

At time t ₀ = 0, the electric motor is switched on under load. The load is then kept constant in the time interval t ₀ <t <t ₁ . The rotational speed is brought by the control to the setpoint ω ₀ and held on this. At time t ₁ , the load is increased, the rotational speed decreases for a short time until it levels off again after a certain time by the setpoint ω ₀ . At the time t ₂ , the load is reduced, the rotational speed increases briefly until it settles again after a certain time by the setpoint ω ₀ . At time t ₃ , the actuator connected to the motor is in abutment, so that it can not be rotated further and the load on the motor 20 increases sharply. The rotational speed decreases sharply and no longer exceeds the minimum value ω _min . The power supply for the motor 20 is turned off in this case.

An advantageous type of auto-commutation will be explained with reference to FIG. 3 using the example of a motor 20 with two coils A and B. The upper curve 45a shows the voltage Va in the coil A as a function of the time t, the lower curve 45b shows the voltage Vb in the coil B as a function of the time t. The dashed curve 46a or 46b is sinusoidal and represents the voltage that the permanent magnet rotor 23 induces in the respective coil A and B, respectively. Both coils A, B are alternately energized. The respective non-energized coil is used as a measuring coil to determine the time of the zero crossing (t ₉ ) of the (induced) voltage.

In the example according to FIG. 3, the voltage in the coil A after the first energization 47 and discharge 48 corresponds to the voltage induced by the rotor 23. If this changes sign (time t ₉ in Fig. 3), a certain time is waited and then the energization in coil B off or switched on in coil A (time t ₁₀ in Fig. 3). Coil B now serves as a measuring coil. When the voltage in the coil B changes the sign (time t ₁₁ in Fig. 3), a certain time is waited and then the energization in coil A off or switched on in coil B (time t ₁₂ in Fig. 3).

The time difference t ₁₁ -t ₉ is inversely proportional to the instantaneous rotational speed of the rotor 23 and can thus be used to determine the actual value in the control according to the first embodiment.

The time difference t ₁₀ -t ₉ or t ₁₂ -t ₁₁ corresponds to a commutation delay (or a commutation lead, if it is positive). It can be fixed, so that t ₁₀ -t ₉ and t ₁₂ -t _{11 are} constant, whereby zero is also conceivable. It is also possible, in addition to the regulation of the rotational speed ω, to also regulate the time difference t ₁₀ -t ₉ or t ₁₂ -t ₁₁ , so that a more refined control of the rotational speed ω or of the torque results.

The method of auto-commutation given here has the special advantage that no additional sensors like Hall sensors needed to be the current position or rotational speed of the rotor 23 to detect. The Control electronics can thus for the most diverse Types of electric motors, in particular also sensorless motors, are used.

2nd embodiment

The motor 20 is by means of the control electronics 30 in Step mode operated and thus becomes a stepper motor used. The coils 22a, 22b are provided with a predetermined, fixed clock according to a specific scheme energized. In the alternating energization of the coils 22a, 22b rotates the field strength direction of the electromagnetic Field in the stator windings and thus generates a rotating field.

The power of the motor 20 becomes dependent on the load regulated. As a controlled variable, the load angle of the rotor 23 used.

The load angle is the angle between the rotating field and the Position of the rotor 23. Are the effects of friction as considered negligible, so is at unloaded Motor shaft of the load angle is essentially zero. at Loading the position of the rotor 23 lags behind the rotating field (or precede it if the load is positive). If no step losses occur, then the load angle lies between 0 degrees and 180 degrees.

With reference to FIG. 4, the control according to the second embodiment will be explained. The engine 20 includes two coils A and B and is in half-step mode ("half-step mode"), i. it flows after everyone second half step only in one of the two coils A, B a Current according to the scheme AB / B / A'B / A '/ A'B' / B '/ AB' / A / AB, where at A 'and B' the current flows in the opposite direction.

• Nach dem Einschalten der Bestromung von Spule B wird eine vorbestimmte Zeit gewartet, bis zumindest in Spule A kein Strom mehr fliesst und die Spannung in Spule A der vom Rotor induzierten Spannung ("elektromotorische Kraft") entspricht.
• Dann wird das Vorzeichen der elektromotorischen Kraft in Spule A eine bestimmte Anzahl mal nacheinander gemessen (z.B. zehnmal, wobei sich beispielsweise folgende Reihe der Vorzeichen ergibt: +,+,+,-,-,-,-,-,-,-).
• Die Anzahl positiver und negativer Vorzeichen gibt Aufschluss über die momentane Position des Rotors 23. (In Fig. 4 durch den Pfeil 51 angedeutet). Da die momentane Richtung des Drehfeldes bekannt ist (in Fig. 4 durch den Pfeil 52 angedeutet), kann daraus der Lastwinkel zumindest annähernd bestimmt werden. (Je nach der Anzahl der gemessenen Vorzeichen kann die Auflösung verbessert werden.) Überwiegen die Anzahl positiver Vorzeichen, so ist der Motor 20 stark belastet und der Rotor 23 hinkt dem Drehfeld stark nach (grosser Lastwinkel). Überwiegen die Anzahl negativer Vorzeichen, so ist der Motor 20 kaum belastet und der Rotor 23 hinkt dem Drehfeld kaum nach (kleiner Lastwinkel).
• Ist der Lastwinkel kleiner als ein vorgegebener Sollwert, wird der Strompegel reduziert, ist der Lastwinkel grösser als der Sollwert, wird der Strompegel erhöht.

While only the coil B is energized, the coil A is used as a measuring coil to measure the load angle. The measurement is carried out as follows:

• After switching on the energization of coil B, a predetermined time is waited until no current flows at least in coil A and the voltage in coil A corresponds to the voltage induced by the rotor ("electromotive force").
• Then, the sign of the electromotive force in coil A is measured a certain number of times in succession (eg ten times, for example, the following series of signs: +, +, +, -, -, -, -, -, -, -).
• The number of positive and negative signs provides information about the instantaneous position of the rotor 23 (indicated by the arrow 51 in FIG. 4). Since the instantaneous direction of the rotating field is known (indicated in FIG. 4 by the arrow 52), the load angle can be determined at least approximately from this. (Depending on the number of measured signs, the resolution can be improved.) If the number of positive signs outweighs, the motor 20 is heavily loaded and the rotor 23 lags behind the rotating field greatly (large load angle). If the number of negative signs outweighs, the motor 20 is hardly loaded and the rotor 23 hardly lags behind the rotating field (small load angle).
• If the load angle is smaller than a predetermined setpoint, the current level is reduced, if the load angle is greater than the setpoint, the current level is increased.

By this regulation, the engine 20 provides the respective just needed power.

• Das Drehmoment bzw. die Motorleistung wird durch die Regelung dem gerade benötigten Wert angepasst. Da bei Kraftfahrzeugen unter normalen Bedingungen für Vs und Ta das benötigte Drehmoment bzw. die benötigte Motorleistung relativ niedrig ist, können die vom Motor erzeugten Vibrationen wesentlich reduziert werden und somit kann ein geräuschreduzierter Betrieb gewährleistet werden. Auch werden die mechanischen Komponenten weniger stark beansprucht.
• Da die Bestromung im zeitlichen Mittel tiefer ist, erhitzen Motor und Ansteuerungselektronik weniger stark, was u.a. zu einer Erhöhung ihrer Lebensdauer führt.
• Mittels der Regelung kann auf einfache Art und Weise die Position der maximal möglichen Verdrehung eines Stellelements detektiert werden, ohne dass zusätzliche Komponenten erforderlich sind.

Unless already mentioned, the method according to the invention and the control electronics according to the invention have the following advantages:

• The torque or the engine power is adjusted by the control to the value just required. Since in vehicles under normal conditions for Vs and Ta the required torque or the required engine power is relatively low, the vibrations generated by the engine can be substantially reduced and thus a noise-reduced operation can be ensured. Also, the mechanical components are less stressed.
• Since the current supply is lower on average over time, the motor and control electronics heat up less, which leads among other things to an increase in their service life.
• By means of the control, the position of the maximum possible rotation of an actuating element can be detected in a simple manner, without additional components being required.

application

Fig. 5 shows an actuator 10 for setting a Actuating element. The actuator 10 comprises a housing cover 61 and a housing bottom 62, in which following Components are included: control electronics 30, electric motor 20 with a drive shaft 64, which with a worm wheel is provided, and one of gears formed reduction gear 65th

The actuator 10 according to FIG. 5 may e.g. for adjustment a flap in a heating, ventilation and / or Air conditioning of a motor vehicle can be used.

Fig. 6 shows schematically an air conditioner in one Motor vehicle. It comprises a radial fan 70, by means of which sucked in outside air and via a filter to Evaporator 71 can be transported. This serves for Cooling and dehumidifying the sucked air. Further points the air conditioner a radiator 72 on to heat the flowing air and a mixing zone 73, in which Cold air from the evaporator 71 and hot air from the radiator 72nd be mixed. At the end of the air conditioning are different Outlets 74a, 74b, 74c through which the mixed Finally, air can enter the vehicle interior. Outlet 74a, for example, leads to the windshield, Outlet 74b to the center nozzles and outlet 74c in the Footwell.

In the air conditioner shown in Fig. 6 is located between the evaporator 71 and the mixing zone 73 a first flap 80 and between the evaporator 71 and the Radiator 72, a second flap 81. The flaps 80, 81 are movably mounted about an axis, so by a corresponding adjustment of the air flow to the mixing zone 73 or to the radiator 72 regulated and finally cold and Warm air in the mixing zone 73 in the desired manner and Can be mixed. The outlets 74a, 74b and 74c are also provided with flaps 84a, 84b and 84c, respectively However, they are usually manually operated.

Fig. 7 shows a cross section through the housing 87 of the Air conditioning with the two flaps 80, 81, each with connected to an actuator 10 and movable about the axis 89 are stored. The left chamber, for example, leads to Mixing zone 73, the right chamber to the radiator 72. The Actuators 10 are connected to the central control unit 14 connected to receive control signals so as to Position of the flaps 80, 81 as a function of sensor data to be able to regulate.

Claims (12)

Control electronics for controlling an electric motor, in particular stepping motor or brushless DC motor, characterized in that it comprises control means (31, 32, 33, 34, 35) which allow the power supply of the motor (20) in dependence on the force acting on the motor Load. Control electronics according to claim 1, characterized in that the control means comprises the following components: an evaluation unit (31, 32, 35) for recurrently determining the deviation of a load-dependent controlled variable from a predetermined desired value; and Adjustment means (33, 34) for adjusting the power supply of the motor (20) in dependence on the deviation. Control electronics according to one of claims 1 to 2, characterized in that with the evaluation unit (31, 32, 35) values for the voltages can be detected and evaluated, which during the rotation of the rotor (23) in the motor windings (22a, 22b) induced be, and preferably based on these values, the respective commutation (t ₁₀ , t ₁₂ ) of the motor windings can be determined. Control electronics according to one of claims 1 to 3, characterized in that the adjusting means comprise a transistor circuit (33) and a pulse generator (34), wherein the pulses are preferably pulse width modulated. Actuator (10) with an electric motor (20), In particular sensorless motor, stepper motor and / or brushless DC motor, and one Control electronics according to one of claims 1 to 4. Method for controlling an electric motor by means of a control electronics according to one of claims 1 to 5, characterized in that the power supply for the motor (20) is adjusted by controlling a controlled variable to a desired value, wherein the controlled variable depends on the load acting on the motor is. A method according to claim 6, characterized in that the rotational speed of the rotor (23) is used as a controlled variable, and the rotor is preferably rotated by autocommutation in rotation. A method according to claim 6, characterized in that the load angle of the motor (20) is used as a controlled variable, and the rotor (23) is preferably set in stepping operation in rotation. Method according to one of claims 6 to 8, characterized in that for determining the actual value of the controlled variable, the voltages which are induced during the rotation of the rotor (23) in the motor windings (22a, 22b) are evaluated. Method according to Claim 9, characterized in that the time difference between zero crossing (t ₉ , t ₁₁ ) of an induced voltage (Va, Vb) and commutation time (t ₁₀ , t ₁₂ ) of the motor windings (22a, 22b) is regulated. Method according to one of claims 6 to 10, characterized in that the power supply is switched off when the actual value of the controlled variable no longer reaches a predetermined value, in particular does not exceed a minimum value. Use of the control electronics according to one of Claims 1 to 4 and / or the method according to one of Claims 6 to 11 for driving an electric motor (20), in particular a sensorless motor, which with a flap (80, 81) in a heating, ventilation and / or Air conditioning system of a motor vehicle is in operative connection.

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